Output voltage estimation of a half-bridge inverter for domestic induction heating applications

The power supplied to a vessel by a domestic induction-heating appliance is strongly dependent on several parameters the designer of the system has no control over: the type and the size of the vessel, misalignments between the pot and the inductor, temperatures, etc. A reliable estimation of the power is essential to ensure that the home appliance works under the expected conditions and the user experience is suitable. Furthermore, any reduction of hardware is totally welcome by consumer-electronics manufacturers. In this work, two methods to estimate the output voltage of a half-bridge inverter without digitizing it with an analog-to-digital converter are proposed and the effects that this estimation has on the power calculation are evaluated. Both methods are implemented and experimentally verified in a real prototype with an FPGA (Field-Programmable Gate Array)

DC-Gain Measurement of the Frequency-to-Output Power Transfer Function based on sidebands for Domestic Induction Heating Applications

This paper analyzes different alternatives to obtain the dc gain of the frequency-to-output power transfer function of a series half-bridge resonant inverter for domestic induction heating. In this application, a full-wave rectified bus voltage usually feeds the inverter, and a constant switching frequency is applied during each half-period of the mains voltage. This dc gain is the derivative of the output power with respect to the frequency. A finite difference approximation to the derivative can be obtained measuring the output power during two consecutive half-periods of the mains voltage by injecting a small frequency increment in the second one. This paper compares five alternatives to estimate the gain in only one half-period of the mains, what would allow to increase the controller bandwidth. The alternatives are based on the computation of the DTFS of the sidebands. They are off-line implemented and experimentally verified. The proposed method can also be implemented in real time into a digital controller

Reduced-order models of series resonant inverters in induction heating applications

From the controller design framework, a simple analytical model that captures the dominant behavior in the range of interest is the optimal. When modeling resonant circuits, complex mathematical models are obtained. These high-order models are not the most suitable for controller design. Although some assumptions can be made for simplifying these models, variable frequency operation or load uncertainty can make these premises no longer valid. In this work, a systematic modeling order reduction technique, Slowly Varying Amplitude and Phase (SVAP), is considered for obtaining simpler analytical models of resonant inverters. SVAP gives identical results as the classical model-order residualization technique from automatic control theory. A slight modification of SVAP, Slowly Varying Amplitude Derivative and Phase (SVADP) is applied in this paper to obtain a better validity range. SVADP is validated for a half-bridge series resonant inverter (HBSRI) and for a high- order plant, a dual-half bridge series resonant inverter (DHBSRI) giving analytical second-order transfer functions for both topologies. Simulation and experimental results are provided to show the validity range of the reduced-order models

Implementación en FPGA de un sistema de medida de impedancia armónica de circuitos resonantes en serie basado en el algoritmo lock-in

En esta ponencia se presenta un sistema digital implementado en FPGA (field programmablegate array) cuya función es la medida en tiempo real de la impedancia del primer armónico deuna carga de una cocina de calentamiento por inducción. La etapa inversora de la cocinaimplementa la topología semipuente resonante serie de media frecuencia (25 kHz – 75 kHz)cuyo circuito de carga consiste en un condensador en serie con el sistema inductor‐recipiente(inductor planar acoplado con un recipiente). En una primera aproximación, la impedancia delcircuito puede modelarse como una red equivalente R‐L‐C, sin embargo, la impedanciaequivalente depende de múltiples factores tales como el material del recipiente, alineamientoentre el recipiente y el inductor, temperatura o frecuencia de trabajo. Por dicha razón, unacaracterización en tiempo real de la carga es deseable para realizar un correcto control de laetapa inversora. El sistema de identificación calcula la impedancia del primer armónico de lacarga aplicando el algoritmo lock‐in de fase dual a la corriente que atraviesa el inductor y a latensión de salida del inversor. Dicho algoritmo ha sido descrito en VHDL (very high speedintegrated circuit hadware description language) e implementado en una FPGA de Xilinx. Laprecisión del algoritmo ha sido verificada mediante simulación a través de una herramienta desimulación mixta (analógica‐digital). Finalmente, el sistema ha sido verificadoexperimentalmente

Sistemas dinámicos y aplicaciones

La Teoría de sistemas dinámicos abarca una gran variedad de problemas, técnicas y aplicaciones, y ha crecido en estrecha vinculación con otras disciplinas. Este proyecto se propone avanzar en el conocimiento referido a algunas líneas de investigación y sus aplicaciones: - Análisis de oscilaciones en sistemas dinámicos. - Modelos no lineales y dinámica de poblaciones. - Sistemas dinámicos no lineales, discretos y determinísticos, vinculados a sistemas de tiempo real.Eje: Procesamiento de señales y sistemas en tiempo realRed de Universidades con Carreras en Informática (RedUNCI

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

AVONET: morphological, ecological and geographical data for all birds

Functional traits offer a rich quantitative framework for developing and testing theories in evolutionary biology, ecology and ecosystem science. However, the potential of functional traits to drive theoretical advances and refine models of global change can only be fully realised when species‐level information is complete. Here we present the AVONET dataset containing comprehensive functional trait data for all birds, including six ecological variables, 11 continuous morphological traits, and information on range size and location. Raw morphological measurements are presented from 90,020 individuals of 11,009 extant bird species sampled from 181 countries. These data are also summarised as species averages in three taxonomic formats, allowing integration with a global phylogeny, geographical range maps, IUCN Red List data and the eBird citizen science database. The AVONET dataset provides the most detailed picture of continuous trait variation for any major radiation of organisms, offering a global template for testing hypotheses and exploring the evolutionary origins, structure and functioning of biodiversity

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

The Cholecystectomy As A Day Case (CAAD) Score: A Validated Score of Preoperative Predictors of Successful Day-Case Cholecystectomy Using the CholeS Data Set

Background Day-case surgery is associated with significant patient and cost benefits. However, only 43% of cholecystectomy patients are discharged home the same day. One hypothesis is day-case cholecystectomy rates, defined as patients discharged the same day as their operation, may be improved by better assessment of patients using standard preoperative variables. Methods Data were extracted from a prospectively collected data set of cholecystectomy patients from 166 UK and Irish hospitals (CholeS). Cholecystectomies performed as elective procedures were divided into main (75%) and validation (25%) data sets. Preoperative predictors were identified, and a risk score of failed day case was devised using multivariate logistic regression. Receiver operating curve analysis was used to validate the score in the validation data set. Results Of the 7426 elective cholecystectomies performed, 49% of these were discharged home the same day. Same-day discharge following cholecystectomy was less likely with older patients (OR 0.18, 95% CI 0.15–0.23), higher ASA scores (OR 0.19, 95% CI 0.15–0.23), complicated cholelithiasis (OR 0.38, 95% CI 0.31 to 0.48), male gender (OR 0.66, 95% CI 0.58–0.74), previous acute gallstone-related admissions (OR 0.54, 95% CI 0.48–0.60) and preoperative endoscopic intervention (OR 0.40, 95% CI 0.34–0.47). The CAAD score was developed using these variables. When applied to the validation subgroup, a CAAD score of ≤5 was associated with 80.8% successful day-case cholecystectomy compared with 19.2% associated with a CAAD score >5 (p < 0.001). Conclusions The CAAD score which utilises data readily available from clinic letters and electronic sources can predict same-day discharges following cholecystectomy